In a blockbuster deal estimated at over one billion dollars, Allstate has gone public with their plans to purchase both Esurance Insurance Co. and Answer Financial from White Mountains Insurance Group.

According to the National Association of Insurance Commissioners (NAIC), the deal will bring a huge chunk of the insurance market to Allstate's front door. Last year, Allstate wrote nearly $17 billion in car policy premiums, amounting to about a 10 percent share of the U.S. market. During the same period, White Mountains wrote $986 million, about 0.6 percent of total auto premiums written last year.

By purchasing the two companies from White Mountains, Allstate plans to update its online presence as well as offer its customers informational and quote comparison services.

Esurance has established itself as a key player in shopping for and purchasing auto insurance online. Since their introduction in 2005, Esurance has managed to provide cut-rate auto insurance in 30 states, and will surely bring more clients to the Allstate family.

Although Answer Financial doesn't actually write auto insurance policies, the company is a valuable acquisition for Allstate. By providing informational and quote comparison services, Answer Financial has a lot to offer Allstate and its customers.

"Esurance will expand our ability to serve customers that are more self-directed but still prefer a branded product," Allstate representatives said in a press release about the acquisition. "Answer Financial will strengthen our offering to individuals who want to be offered a choice between insurance carriers and are brand-neutral."

At the end of the trading day, the announcement made waves in the auto insurance industry with Allstate's stock finishing up about a tenth of a percent, while White Mountains stock jumped about 15 percent.

—AJ Register